import java.util.Scanner;

public class BYZ2 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = 26;
        int b = a * a;
        int dp = 2021 - a - b;
        int c = 0;
        for (int i = 0; i <26 ; i++) {
            for (int j = 0; j <26; j++) {
                for (int k = 0; k < 26; k++) {
                    c++;
                    if (c == dp) {
                        char c1 =(char)(i+65);
                        char c2 =(char)(j+'A');
                        char c3 =(char)(k+'A');
                        String sv = String.valueOf(c1 + c2 + c3);
                        System.out.println(sv);
                    }
                }
            }
        }
    }
}
